Antennas are often designed to be directional, and must be correctly pointed or aimed when installed. Therefore, mounts for attaching antenna to fixed structures, such as buildings or cell towers, can provide power-actuated steering adjustment. The adjustments can include power actuated steering adjustment to the antenna mounts, and can include power-actuated adjustment to a “remote electrical tilt” or “RET” motor/actuator located inside the antenna. The RET motor/actuator can change the phase of each antenna element, causing the antenna-beam to “tilt” without tilting the physical antenna. The power actuated adjustment, though, can require delivery of direct current (DC). A complication is that antenna masts often support a plurality of antennas, fed by a corresponding plurality of radios located, for example, at the base of the antenna mast. Providing a dedicated transmission line, e.g., coaxial cable for each and every one of the radios to feed its corresponding antenna(s) is generally not practicable. Therefore, a particular multiplexing can be employed, using combiners and de-combiners, to put all of the radio feeds onto a common coaxial cable.
The multiplexing techniques, however, can complicate adjustment of the multiple antennas. A reason is that DC current delivery techniques, for providing DC current to the adjustment mechanism of a given radio's antenna include inserting DC current into the multiplexer input port that is normally fed by the radio. A technique to avoid the DC current from interfering with other radios and other antennas is to insert DC block devices known as “DC blocks” into all of the feed ports, at the antenna base and at the antenna mast top, except for the port feeding the antenna for which adjustment is desired. The present technique is time consuming, costly, dangerous and is prone to error. For example, installing the DC blocks at the antenna mast top requires a technician to climb the antenna mast to the antenna top. This requires significant resources, time and money.
A solution for providing DC current, through multiplexed antenna feeds, to a desired antenna mechanism without causing current to flow into other radios or to other antenna faces, and without requiring climbing antenna masts is needed.